1. Field of Invention
The present invention relates to an electronic circuit, an electro-optical device, a method for driving the electro-optical device, and an electronic apparatus.
2. Description of Related Art
Recently, much attention has been given to display device using an electro-optical device including an organic EL element. For this type of electro-optical devices, various types of analog-gray-scale-modulation methods can be used as a driving method for controlling the gray scale of the organic EL element. According to one of the analog-gray-scale-modulation methods, the voltage between the gate and source of a driving transistor can be rendered as the threshold voltage thereof for driving, the driving transistor being provided for transmitting a current to the organic EL element. According to this method, a voltage (a data voltage) transmitted from a DA-converter circuit according to the luminance gray scale is held in a holding capacitor of a pixel circuit. The data voltage charged in the holding capacitor is transmitted to a gate terminal of the driving transistor formed of a thin-film transistor (TFT). The driving transistor transmits a drive current with a value corresponding to the data voltage to the organic EL element.
It is difficult to form the DA-converter circuit with precision by using the thin-film transistor (TFT) forming the pixel circuit, the DA-converter circuit being used in the case where the analog-gray-scale-modulation method is applied. Therefore, in general, the DA-converter circuit is formed by using an external IC driver.
However, the electrical power consumption of the DA-converter circuit formed of the external IC driver is larger than that of a TFT-driver circuit formed on a display panel. In this case, a digital-gray-scale-modulation method may be used according to the reason described below. Since the digital-gray-scale-modulation method does not require the use of the DA-converter circuit for generating a multilevel value (an analog value), the electrical-power consumption can be reduced. However, the display quality obtained according to the digital-gray-scale-modulation method is lower than that in the case where the analog-gray-scale-modulation method is applied.